window has to come out, and the window style has to be for the rubber piece...as far as I know, they part number for the windshield is different.
the rubber molded ones started in late 94. they're for the air bag deployment...when that happens, the window will bust out rather than holding it in and potentially causing damage to the driver.
don't even attempt to remove the windshield yourself. a first-timer should try it on something that's junk, and personally, I've had a couple windshields out and will always pay to have it done...around $100 bucks here to swap in a used windshield, that's including removing the one from the donor truck. $180 for a brand spanking new windshield.